A silicon thin film is used for applications such as solar cells and semiconductors, and this silicon thin film has been previously prepared by a vapor deposition film-forming method (CVD method) using monosilane as a raw material. Recently, in place of the CVD method, a new production method using cyclic hydrogenated silane has been focused. This production method is a coating film-forming method (liquid process) in which a hydrogenated polysilane solution is applied to a substrate, followed by calcination, and cyclopentasilane is used as a raw material for the preparation of the hydrogenated polysilane solution. Cyclopentasilane is commercially available, and has been reported to be hydrogenated polysilane by UV irradiation (Non-Patent Document 1). However, cyclopentasilane requires multistep synthesis using an expensive water-reactive reagent and a purification step for its production, and thus is very expensive.
Therefore, the present inventors have focused on cyclohexasilane as an alternate material for cyclopentasilane. As the synthesis method of a cyclohexasilane, Hengge et at report that a cyclohexasilane can be synthesized using diphenyldichlorosilane as a starting material (Non-Patent Document 1).